Limiting Reagents and Percent Yield
Definitions:
Limiting Reagents: Reactant which is completely used up in the reaction
Excess Reagent: Reactant which has some left over after the reaction has completed
Percent Yield: actual product made divided by the theoretical amount of product possible, multiplied by 100%
Problem 1:Ender is building rafts. He builds the frames and then connects in store bought oars (2 each), a rudder (1
each) and a seat (1 each). He has 5 oars, 3 rudders, and 2 seats.
a) How many rafts can he build?
b) What here is analogous to the limiting reagent?
c) What is analogous to the excess reagent, and how many are left over?
d) Write the analogous chemical reaction if Frames=F, Oars=O, Rudder= R and Seat=S.
Problem 2: Valentine is preparing sushi for her family. The recipe calls for 2.00 cups of rice, 1 avocado, 4 sheets nori
and 4 crabsticks. Each batch makes 6 pieces. Valentine has 10.00 cups of rice, 3 avocados, a dozen nori and 8 crabsticks.
a) What is the limiting reagent?
b) How many pieces of sushi can she make?
c) How much leftover “excess reagent” is there?
d) If during the preparation process, a squirrel attacks and ruins two of her sushi pieces, what is the percent yield?
Reminder: percent yield is the actual yield divided by the theoretical yield, then multiplied by 100%.
Limiting Reagents and Percent Yield
Problem 3:
Peter is making nitroglycerin (C3H5N3O9) according to the following reaction:
.
If he has 10.0 g of glycerin and 8.0 g of nitric acid, answer the following questions.
a) What is the limiting reagent?**
b) How many grams of nitroglycerin can he make?**
c) How many grams of the excess reagent is left over?***
Problem 4: Naming (If there is time: There likely won’t be). *
a) Provide the name for Na2SO4
b) Provide the name for HClO4 (in water)
c) Provide the formula for lead (II) nitrate.
d) Provide the formula for ammonium phosphite
Limiting Reagents and Percent Yield
Challenge Problem: ***** (Note the problem itself isn’t that difficult, but the lack of information I give you requires you
to do some looking up, a bit of assumptions of information, and a bit of conversions you may not have seen recently. Given
this it isn’t exactly testable in the format I’ve provided it to you, however, with more information, or say asking you about
reacting pure glucose (with the chemical formula and chemical equation given) ect……I could ask a similar question). There
isn’t one exact RIGHT answer for this. I’ll post up my solution, but you may find yours is a bit different. It’s a challenge
question, such ambiguity is acceptable. If you have questions about whether your process was correct, come talk to me
and we’ll look at it together.
First, watch this video. https://www.youtube.com/watch?v=txkRCIPSsjM . Cool huh?
Now calculate the minimum amount of potassium chlorate that you would need to ensure that all the sugar in the gummy
bear is reacted. Then calculate how much of the products will be present. State any assumptions you make and whether
it is likely to be correct.
Hints:
You’ll need to know what the potassium perchlorate reacts with in the gummy bear.
You’ll need to write the balanced reaction for that.
You’ll need to figure out how much of the reactant is present in a gummy bear. (this is the main reason there isn’t one
CORRECT answer, the brand of gummy bear will matter here ).
From here you will work the problem in a
Limiting Reagents and Percent Yield